This invention relates generally to the field of fluid displacement apparatus, and more particularly, is directed to a method and apparatus for adjusting the angular relationship between the spiral elements of a scroll type fluid displacement apparatus.
Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 (Creux) discloses such a device which includes two scroll members each having a circular end plate and a spiroidal or involute spiral element. The scroll members are maintained angularly and radially offset so that both spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative oribtal motion of the scroll members shifts the line contacts along the spiral curved surfaces and, therefore, the fluid pockets change in volume. since the volume of the fluid pockets increases or decreases dependent on the direction of the orbiting motion, a scroll type fluid displacement apparatus is applicable for compressing, expanding or pumping fluids.
In comparison with conventional compressors of the piston type, the scroll type compressor has certain advantages, such as fewer parts and continuous compression of fluid. Scroll type compressors known in the prior art, however, have the disadvantage that proper adjustment of the angular relationship between the spiral elements is difficult to achieve and maintain. If the angular relationship is not correct, the radial contact points between the spiral elements are not tightly sealed, thereby permitting fluid leakage. As a result, the efficiency of the compressor is significantly reduced.
One solution to the problem of achieving the proper angular relationship between the scroll elements is to reduce the permissible manufacturing tolerances of the component parts. The manufacture of scroll compressor components, however, is already complicated and reducing tolerances would greatly increase manufacturing costs. Another proposed solution is to increase the tolerance of the angular relationship between the spiral elements. Such a solution also has not proved satisfactory.
During the assembly of a scroll type compressor having a ball coupling mechanism, the relative angular relationship between the two scroll members is controlled by the following factors;
(1) the relative angular offset between the fixed scroll elements and the housing; PA1 (2) the relative angular offset between the housing and the front end plate of the housing; PA1 (3) the relative angular offset between the front end plate of the housing and the fixed ring of the ball coupling mechanism; PA1 (4) the relative angular offset caused by the difference between the inner diameter of the hole formed in the fixed ring of the ball coupling mechanism and the outer diameter of the ball; PA1 (5) the relative angular offset caused by the difference between the outer diameter of the ball and the inner diameter of the hole formed in the movable ring of the ball coupling mechanism; and PA1 (6) the relative angular offset between the movable ring of the ball coupling mechanism and the orbiting scroll member.
In order to accomodate these factors, one technique to establish the proper angular relationship between the scroll members is to provide a first hole in the end wall surface of the spiral element of one scroll member and a second hole through the front end plate opposite to the first hole formed in the scroll member. Proper adjustment of the relationship between both scroll members is established by inserting an angle adjusting member through both holes from the outside of the front end plate.
While the above technique may be effective with respect to factors 1-3 listed above, it has not proved effective with respect to factors 4-6.